Laparoscopic surgery, also called minimally invasive surgery (MIS), or keyhole surgery, is a modern surgical technique in which operations in the abdomen are performed through small incisions (usually 0.5-1.5 cm) as compared to larger incisions needed in traditional surgical procedures. Laparoscopic surgery includes operations within the abdominal or pelvic cavities.
In abdominal surgery, for example, the abdomen is usually insufflated with carbon dioxide gas to create a working and viewing space. The abdomen is blown, up like a balloon (insufflated); elevating the abdominal wall above the internal organs like a dome. The gas used is generally CO2, which is common to the human body and can be absorbed by tissue and removed by the respiratory system. It is also non-flammable, which is important because electrosurgical devices are commonly used in laparoscopic procedures. FIG. 1 shows a diagram of a typical laparoscopic procedure, with part of the outer layers of the body not shown so as to show interior detail.
The purpose of insufflation is to create a working space within the body for carrying out surgical procedures which frequently can involve electrosurgery or electrocautery. Lasers are also becoming increasingly popular in modern surgical procedures. The use of these devices tends to create surgical smoke in the working space due to burning of tissue. Smoke evacuation systems which use a discharge limb are commonly used to remove the smoke from the surgical site, so that a surgeon can see what he or she is doing, and so that this potentially harmful material does not remain within the body cavity post-surgery. One end of the discharge limb is connected to or inserted into, a second incision (or sometimes the same incision). A typical smoke evacuation system generally includes a trocar and a cannula at the end to aid insertion into the operative site. The smoke exits the insufflated abdominal area through the discharge limb. The discharge limb may be attached to the end of a laparoscopic instrument so as to provide evacuation close to the site where electrocautery takes place. Usually, the gases and smoke from the body cavity are filtered through a filter to remove particulate matter before they are vented to atmosphere. The filter may also be additionally designed to remove chemicals and any harmful micro-organisms from the surgical smoke. U.S. Pat. No. 5,578,000, U.S. Pat. No. 6,110,259 and U.S. Pat. No. 5,226,939 all describe examples of surgical smoke evacuation systems. Commonly available surgical smoke evacuation systems include, for example, the SmartVac® smoke evacuation system and the SeeClear® MAX smoke evacuation system. The smoke filter is usually located at the other end of the discharge limb from that end which is inserted into the incision.
Commonly, a vacuum source is connected to the other end of the discharge limb—the end furthest from the patient. The vacuum source may be a wall vacuum or a standalone vacuum device. The vacuum creates a negative pressure within the operative site to ‘suck out’ smoke and any excess insufflation gases. In an arrangement where a vacuum source is used, it is usual to position the filter at a point along the conduit generally just upstream of the vacuum source to remove the undesirable contaminants from the evacuated smoke.
Current smoke evacuation systems use plastic tubing (generally PVC tubing), for the discharge limb. The atmosphere within a patient's abdominal cavity is generally humid, and the heat of surgical operations such as electrocautery tends to add to the humidity as the heat causes moisture to evaporate from the patient's internal organs. It has been common practice in laparoscopic surgery to use dry gases. However, it is also desirable for the CO2 or other insufflation gas to be humidified in a similar fashion to how gases are humidified for respiratory therapy—e.g. CPAP or similar. In insufflation applications, the gases are humidified before they are passed into the abdominal cavity. This can help prevent ‘drying out’ of the patient's internal organs, and can decrease the amount of time needed for recovery from surgery.
Smoke evacuation systems are commonly used with insufflation systems. Insufflation systems deliver humidified gases into an incision to create a working space within the body for electrocautery surgery, electro-surgery or laparoscopic procedures. Insufflation systems generally comprise humidifier chambers that hold a quantity of water within them. The humidifier generally includes a heater plate that heats the water to create a water vapour that is transmitted into the incoming gases to humidify the gases. The gases are transported out of the humidifier with the water vapour. The humidification chamber requires a minimum level of water to allow the humidification chamber to adequately humidify incoming gases. Accordingly a health professional or person using the insufflation system needs to keep checking the water level in the humidification chamber and add more water when required. This job can be tedious one and is often overlooked. U.S. Pat. No. 6,802,314 discloses a method of monitoring the level of water in a humidification chamber. The method is implemented on an electronic controller that controls the humidifier heater plate operation and operation of the blower used with the humidifier. The method involves monitoring the temperature of the heater base 102, the temperature of the humidification chamber 103 (or chamber outlet temperature) and the power requirement of the heater base (the amount of power being supplied to the heater base). Thermal conductivity is calculated using the measured values. Thermal conductivity is calculated by the heater base power requirement divided by the heater plate temperature minus the chamber temperature.
The controller compares the calculated thermal conductivity value to a predetermined threshold value which may be experimentally determined at various gases flow rates. The predetermined threshold values can be stored in ROM and be accessible to the controller so that the controller would simply determine the present flow rate of the gases, calculate the value of thermal conductivity, access the table in ROM based on the present flow rate and read out the associated predetermined threshold value. If the calculated thermal conductivity is greater than the thermal conductivity value then the controller would wait a predetermined time before issuing an alarm so that the water level could be topped up without any loss of humidity in the gases flow.
It is an object of the present invention to at least partially help to overcome these problems and other defects in the prior art, or at least provide the public with a useful alternative.
The term “comprising” as used in this specification means “consisting at least in part of”. When interpreting each statement in this specification that includes the term “comprising”, features other than that or those prefaced by the term may also be present. Related terms such as “comprise” and “comprises” are to be interpreted in the same manner.
In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.